Basement a/c question

[richard5933]

I don't have the manual for the exact generator setup I have. The manuals I have are for various close setups but not exact. So, I am working with questionable data.

What I've found is that the model number ending in 67 is set at 10.3kw instead of 12kw with a note stating "adjusted for radiator fan"

Not sure what's going on or why this is so. My set up uses a remote radiator and a remote squirrel fan to cool the generator.

If it's possible to reconfigure the generator to put out 12kw I'd love to find out what's involved.

[luvrbus]

Yep the engine driven fan robs HP so the KW drops with your setup you are probably at 12 kw

[brmax]

Best thing about these new smart phones is you can turn the flash on and reach in and take all kinds of pictures.
Great for tough viewing situations



good day

Floyd

[richard5933]

UPDATE:

After doing lots of research and talking to the guy that services our home's a/c units, here's what I've done...

I opened both basement a/c units and did a visual inspection. Fan motors turned freely, and all wire connections were clean and tight. There is no visible damage or leaks anywhere. Used compressed air to blow the condensing coils - both were relatively clean and now even cleaner. The relay contacts were contained inside a plastic housing that didn't seem keen on being opened, so I left it alone. The interior units are really quite clean and all connections were tight.

All connections at the generator and at the transfer switch were checked. All were tight. No signs of overheating in sight.

I did open the inspection cover at the end of the generator head. The three rings were in great shape and the brushes as well. Connections were tight as far as I could tell.

Finally, I adjusted the governor on the generator to raise the voltage & hz just a tad. At no load it produces 120v @ 61hz. At moderate-to-full load it read 115-117 volts @ 60hz. Previous readings at load were just under 110 volts and 57-58 hz. A manual for a similar system shows low voltage as a cause of short cycling, so hopefully this was the issue.

The a/c units both ran fine today. Both units blow cold and no short cycling yet. Fingers crossed. Of course, the outside temps are not that bad and only in the upper 70s. I'll be able to better test things in the coming days as the temps are expected to be in the 90s.

We're heading to Gillette WY next month for a week and plan on dry camping three nights on the way, so we'll have a chance to test it out more thoroughly then as well.

A replacement generator is on the list for next year, once we figure out the best approach. I think that a 13kw Wrico unit with remote radiator should be able to sit right on the existing slide, although the mounting feet may need moving. But, this is a project for down the road.

If you think of something I've missed, please let me know.

[richard5933]

And now I believe we have the final diagnosis...

The unit runs pretty well, both on shore power and on generator. However, when the temps get high (95+) the unit short cycles. It will run for anywhere from 5-15 minutes and then the low pressure switch shuts off the compressor. We had an HVAC guy come out today and diagnose the unit, and his conclusion is that it's low on refrigerant. Probably has a leak, or possibly it was not filled properly the last time it was serviced (no idea when that was). The problem now is that it is using r12. According to him there is no r12 available in this area. Don't know if it's true or not, but he was unable to do anything. Suggestion was made to have the unit converted to r134, which of course is not something his company does.

It took me weeks to find a guy willing to come out just to diagnose the problem. Now I've got to decide if it's worth moving forward with trying to find someone else to do the repair. The guy that came today said that the unit is much more like a split system found on a convenience store cooler than a mini-split or residential unit. He thought that I might be able to find a commercial refrigeration guy to do the repairs.

The other option is to abandon hopes of having a clean roof and just install the roof a/c in the forward roof vent opening. I really want to keep the bus looking like a bus and putting a roof a/c on top is not at all what we want, but it might be the most practical solution. Of course, I'm not one to choose practical.

[brmax]

I was wondering if any of the relays are visible, and possibly in the commercial size. Meaning do they or any have removeable covers. If so with the electric turned off for that system inspecting the relay for visible issues, like loose wires and or burnt contact points.

Good day there

Floyd

[richard5933]

The tech that was here today put his gauges on the system. He was able to verify that the problem is with low refrigerant. Under mild weather conditions (75-80 degrees) it runs slightly low pressure on the low-pressure side. As the ambient temp increases and the unit works harder the low-pressure sides keeps dropping slowly until the low-pressure cutoff switch shuts things down. Once the pressure equalizes it will run again for a while, and then the pressure drops...

Doesn't seem like the problem is with the relays or low-pressure switch itself.

I've found a small commercial refrigeration outfit in town that seems willing to come take a look next week. We'll see if they are able to follow through. Maybe they can find the leak (if there is one) and get their hands on some r12 to top it off.

[eagle19952]

Are the caps on the pressure check ports ? I have seen those (the valves in side) work under pressure rise and fall leak ever so slowly...
I would definitely go where I could get some R-12....
The system must be ancient, are you sure it isn't R-22 ?
wonder if this works...https://www.ebay.com/i/122508929925?chn=ps

[richard5933]

Are the caps on the pressure check ports ? I have seen those (the valves in side) work under pressure rise and fall leak ever so slowly...
I would definitely go where I could get some R-12....
The system must be ancient, are you sure it isn't R-22 ?
wonder if this works...https://www.ebay.com/i/122508929925?chn=ps

Am I sure it's not r22? No.

The tech hooked up his gauges, and based on the pressure settings his best guess is that it's got r12. He also based that on the low-pressure differential switch. All this means nothing to me, so I'm going based on what he said. A photo of the switch is attached - if someone can help me identify the type of refrigerant it would be helpful.

Is there a way to tell for certain? There are no visible labels or markings on the unit.

[richard5933]

Here's a photo of the compressor ID plate as well as the overall condensing unit. From what I can find in the online Copeland information, it's likely r12. Not the best news, since that most likely means that it would have to be switched to r134, if that's even possible. I'm working with a guy that hopefully can come to look next week. Of course, every a/c tech immediately yells about how busy they are, so it's hard to get one to come out right now.

Model number on the compressor is: KAJ3-0100-CAA-

What's most impressive is that it looks like they still make the thing, after 44 years. Actually, most impressive is that it blows cold still, at least till the pressure drops.

[oldmansax]

Richard, it's very easy to tell if it's R12 or R22. I worked on a lot of unknown equipment when I owned a commercial refrigeration business.

The only caveat is the bus MUST be the same temperature inside and out. I would open bus windows and turn on all AC systems to FAN ONLY for a few hours before I test. After temperature has equalized inside and out, (meaning the temp of the inside evaporators and outside compressors/condensers/piping are all the same) attach gauges to the system and check the pressure. That will tell you the kind of refrigerant. for example, R22 @ 70F = 121.5 PSI. R12 @ 70F = 70.2 PSI. As you can see, that is a vast difference. You can Google "R22 PT chart" and "R12 PT chart" for charts with all the temps listed.

FYI, most CruiseAir systems of that era used R22, which any HVAC company should have. I betting yours did too.

TOM

[oldmansax]

Richard

I should have added one thing. If that system use R22, it should be charged to 15F superheat. R12 should be 10F superheat. If your HVAC guy appears confused, get another guy. Again, I'm pretty sure you have an R22 system.

TOM

[richard5933]

Richard

I should have added one thing. If that system use R22, it should be charged to 15F superheat. R12 should be 10F superheat. If your HVAC guy appears confused, get another guy. Again, I'm pretty sure you have an R22 system.

TOM

Thanks Tom for the info. I did find another guy to look at the system - this one is from the world of commercial refrigeration. From what I've been able to determine, the system we have is NOT a Cruisair unit at all. It looks like Custom Coach used condensing units originally designed for use in commercial applications, like coolers and such. The new HVAC guy is coming Tuesday. His information (based on the compressor & condensing unit) shows that we've got r12. When I researched on the Copeland site I found the same. He'll verify when he comes out.

I hope that he finds it's really r22, as that's still easily available. If it is r12 I hope that he can find the leak, fix it, and then find some r12 to refill the system. Lots easier and much less expensive than trying to change refrigerant. I'll update after he comes Tuesday.

[richard5933]

Today the guy came out to look at the system. Just the kind of HVAC guy I needed too - he works on his own in his own company, and he has experience with both residential and commercial systems.

Seems that what Custom Coach did was use a commercial split system, just like you'd find cooling a large walk-in cooler, to cool the bus. Actually, two of them. The condensing units in the bays use heavy-duty 115v compressors, which he says are work horse compressors and should last years more.

The front system that was shutting down after a while was somewhat of a mystery. Some of the pressure/temps were spot on, others not so much. The one that worried him was actually the high pressure, and his suspicion was that the compressor was shutting down when the compressor reached it's internal high pressure/temp safety shut off point. The system was supposed to have r12 in it as refrigerant, but the pressures (especially the high pressure) were not correct. He tried to evacuate some of the refrigerant to see if there was too much. Didn't help. Then he evacuated the system, blew it out with nitrogen, evacuated again, changed the dryer/filter, and refilled with an r12 replacement that is supposed to be compatible with the oil in the system. His hunch was that there was a "non-compressible" in the system - either air or some other contaminant introduced by someone working on the system in the past. Presence of something like this would act to essentially downgrade the effectiveness of the condensing coil and raise the high pressure.

After the work he did, the system has been running with no problems so far. It's making cold (very cold) air and cycling on/off with the thermostat as it should.

While he was here, he checked the rear unit. It had bubbles in the sight glass so he topped off the refrigerant. Looks like we might have a very slight leak there, but not one that could be confirmed today.

We're going to run the systems on our trip over the next few weeks and see how things go. Good news is that the repair guy says that all the parts are still around, more than we'd need to totally rebuild the system if necessary. He was actually impressed with the quality of parts Custom Coach used to build the system.

That's all for now.

[Oonrahnjay]

...  Good news is that the repair guy says that all the parts are still around, more than we'd need to totally rebuild the system if necessary. He was actually impressed with the quality of parts Custom Coach used to build the system.

That's all for now. 

      Sorry you've had problems with a major system, but -- if you have a problem -- this is about as good news as you can get.   Good luck from here on out.